BACKGROUND OF THE INVENTION
1. Field of the Invention
[0001] The present invention relates to compressor lip seals. More particularly, the present
invention is directed to a shaft wear sleeve for protecting a crankshaft from excessive
wear caused by lip seal friction.
2. Background Art
[0002] Refrigeration systems, such as the type used in transport refrigeration equipment,
include, in the simplest form, a compressor, a condenser, an expansion device and
an evaporator serially interconnected to form a closed refrigeration circulation path.
In systems that use a reciprocating type compressor, these systems must be lubricated
by a lubricating oil which mixes with the refrigerant being compressed therein.
[0003] A typical reciprocating compressor includes a piston reciprocating within a cylinder
for mechanically compressing gaseous refrigerant. Appropriate manifolds and valves
are provided to allow gas to be drawn into the cylinder during the down stroke of
the piston and to be compressed during the up stroke.
[0004] Oil is used in such compressors to lubricate the various parts and interfaces there
between. To maintain refrigerant pressure within the compressor in an open drive configuration
where the drive is external to the compressor, a mechanical shaft seal is used. The
compressor oil pump deploys an oil film to seal against the leakage of pressurized
gas and to lubricate the faces of the seal during operation. For example, mechanical
shaft seals are used on the crankshaft of the compressor where the crankshaft exits
the compressor crankcase in the vicinity of the gland plate. Crankshafts of such compressors
may also employ additional seals, typically a lip seal, for keeping external contamination
out of the compressor. Accordingly, lip seals are usually the last line of defense
of the internal workings of the compressor and are external to the mechanical shaft
seal and most typically located at the gland plate assembly.
[0005] Lip Seals are usually formed from a material that will endure the constant rotation
of crankshafts. The lip seal material is resilient to the rotational motion and incorporates
a radial spring behind the lip that forces it into contact with the crankshaft under
operation. This continuous contact and rotational motion demands an improved shaft
surface both in hardness and surface quality (roughness) to withstand premature degradation
of the lip seal / crankshaft interface. Because of this, in the prior art, lip seals
have the tendency to wear down the crankshaft at the areas of contact with the shaft
if the shafts are not sufficiently hardened and machined to an acceptable surface
quality. The wear on the crankshaft from the lip seal can form a clearance path from
the machining action. This condition can lead to the intrusion of dirt into the compressor
cavity, damaging the inner mechanisms of the compressor, and/or allowing excessive
leakage of oil to the compressor exterior, and more significantly can lead to required
shaft replacement, an expensive and potentially very laborious job.
SUMMARY OF THE INVENTION
[0006] It is an object of the present invention to improve the life of compressor crankshafts.
[0007] It is a further object of the present invention to provide a crankshaft design to
prevent shaft wear due to the lip-seal interface and accordingly increase crankshaft
life and reduce compressor maintenance.
[0008] These and other objects of the present invention are achieved according to the crankshaft
of the present invention for use in a compressor that incorporates a lip seal. The
crankshaft includes a first material forming the crankshaft, an area on the crankshaft
that engages the lip seal, and protection for the crankshaft from wear due to frictional
contact with the lip seal. The protection includes a secondary material added to the
crankshaft causing a hardened surface of the crankshaft at the area. The protection
is preferably in the form of a wear sleeve on the crankshaft. The wear sleeve is formed
from a second material which wears less than the first material while in contact with
the lip seal and the wear sleeve is formed separate from the crankshaft and removable
for replacement.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009]
FIG. 1 is a schematic, partially cross-sectional view of a reciprocating compressor
incorporating the device of the present invention;
FIG 2 is an enlarged, partially cross-sectional view of the crankshaft seal area of
FIG. 1, including the lip seal;
FIG. 3 is a further enlarged view of the crankshaft, shaft seal and lip seal mechanisms;
and
FIG. 4 is a simplified view of the shaft and perspective view of the wear sleeve,
showing their assembly, according to the principles of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0010] The invention as described herein will refer to a reciprocating compressor for use
with an air conditioning or refrigeration system. Although this compressor is shown
in a configuration and described relative to incorporation with a refrigeration circuit
within an air conditioning system or a refrigeration system it is to be understood
that this method of oil collection, lubrication and diversion is equally applicable
to other types of compressors, pumps and other applications.
[0011] Referring now to FIG. 1, shown is a compressor 10 including shell 12. Working pistons
14 are mounted for reciprocating movement within cylinders 16. Each piston is connected
to crankshaft 18 via a connecting rod 20. Connecting rod 20 is secured around offset
portion 22 of crankshaft 18. Crankshaft 18 includes counterbalance 24 for balancing
the rotational irregularities in the crankshaft. The crankshaft is mounted and rotates
within sleeve 28 and extends through shaft seal cavity 26 of housing 12.
[0012] Referring to FIG. 2 and 4, the crankshaft seal mechanism 31 is shown in greater detail
at the point where the housing 12 is exited by the crankshaft. The crankshaft 18 passes
through the mechanical shaft seal spring assembly 45, shaft seal faces 29 and 33,
gland plate 32 and lip seal 38 having wear surfaces 39. As shown in FIG. 3, a gland
plate gasket 35 is used to prevent seepage between the housing and the gland plate.
The face seal 33 is substantially cylindrical in shape and includes an O-ring 36,
which holds it stationary within inner diameter A of the gland plate 32. The lip seal
38, secured in gland plate 32 adjacent to but spaced from diameter A, in smaller diameter
B, has the function of preventing dirt from entering the shaft seal cavity.
[0013] The crankshaft seal mechanism further includes a cylindrical body 44 formed from
a resilient material, using oil between it and the crankshaft to act as a refrigerant
seal. The spring 45 wrapped around the exterior of the body 44 and resting against
the crankshaft seal thrust face 43 provides axial loading between the two shaft face
seals 29 and 33.
[0014] The invention as provided herein operates to protect crankshaft 18 from excessive
wear due to frictional contact with the lip seal 38. Accordingly, the crankshaft 18,
in the preferred embodiment, includes a material added thereto having a hardened surface
relative the crankshaft, and in particular, a replaceable wear sleeve 48 which is
formed separately from the crankshaft, and is attached to the crankshaft in the area
49 of contact with lip-seal 38. The wear sleeve is cylindrical in shape as shown in
FIG. 4, and fits over and is secured to crankshaft 18, which has a reduced diameter
portion 50 machined to receive the wear sleeve. The wear sleeve may be attached to
the shaft in known manners such as through adhesive bonding, welding or force fit
sizing. The wear sleeve may also be in multiple segments and attached through welding
or adhesive bonding. The wear sleeve is preferably formed from a hardened steel, having
a hardness greater than that of the crankshaft 18 and at an acceptable hardness level
described by the lip seal manufacturer. The wear sleeve is also produced in such a
manner as to achieve an acceptable surface quality (roughness), a secondary requirement
of the lip seal manufacturer.
[0015] While the invention has been described in reference to a preferred embodiment and
a particular type of compressor, it is to be understood by those skilled in the art
that modifications and variations can be effected within the spirit and scope of the
invention and the invention could be applied to different types of compressors or
other mechanisms incorporating similar type shaft seals.
1. A crankshaft (18) for use in a compressor or other machine that incorporates a lip
seal (38), comprising:
a first material forming the crankshaft (18);
an area on the crankshaft that engages the lip seal (38); and
means for protecting the crankshaft (18) from wear due to frictional contact with
the lip seal (38).
2. The crankshaft according to claim 1, wherein said means for protecting comprises a
secondary material added to said crankshaft causing a hardened surface of the crankshaft
(18) at said area.
3. The crankshaft according to claim 1, wherein said means for protecting comprises a
wear sleeve (48) on the crankshaft (18).
4. The crankshaft according to claim 3, wherein said wear sleeve (48) is formed from
a second material which wears less than said first material while in contact with
the lip seal (38).
5. The crankshaft according to claim 3 or 4, wherein said wear sleeve (48) is formed
separate from said crankshaft (18) and removable for replacement.